Study Of High-temperature Properties Research Articles

Study of High Temperature Properties of AlSi10Mg Alloy Produced by Laser-Based Powder Bed Fusion

Additive manufacturing of Al alloys can represent an interesting solution for high-performance components in various industrial fields, as for instance the automotive and aerospace industry. Often, for these applications, the alloys are required to withstand exposure to high temperatures. Therefore, the investigation of the evolution of material properties with increasing temperature is of utmost importance in order to assess their suitability for this kind of applications. In the present study, tensile properties at high temperature were investigated for an AlSi10Mg alloy. Samples were manufactured by laser-based powder bed fusion in horizontal and vertical direction in order to examine the influence of building direction on material behavior. The samples were tested in as-built condition and after exposure to high temperature. Tensile tests were performed up to 150 °C and the effect of holding time at the test temperature was evaluated. Furthermore, the alloy was characterized by mechanical spectroscopy in order to evaluate the behavior of dynamic modulus with temperature and, thus, to provide a comprehensive characterization of the material behavior. It was found that the peculiar microstructure of the alloy produced by additive manufacturing is responsible for good high-temperature strength of the material up to 150 °C. The material also exhibits a good thermal stability even after holding at test temperature for 10 h.

Valence Electron Theoretical Calculation of Austenite Binding Energy

It is of great significance to calculate the binding energy of austenite for the study of high temperature properties of austenite. In this paper, the austenite binding energy was calculated using Yu Ruihuang’s empirical electronic theory. Firstly, according to the electronic structure and composition design of the austenitic unit cell alloy, the bond name of the covalent bond can be written, the equivalent bond number can be calculated, the log(ra) equation can be established, and the nA equation can be established too. Considering the austenite at elevated temperature in the 3d track of Fe’s t state, there must have more valence electrons, those forms the equivalent p’ electrons, so Fe must be of type B hybrid. The austenite is selected in the 11th order of B-type hybridization, and the theoretical bond length and its difference with experiment bond length are respectively calculated. When the austenite is in the 11th order of the B-type hybrid, the bond length difference obtained by the above calculation method is less than 0.05 Å, so that the above calculation is satisfactory within the first-order approximation range. According to the above method, the 12th order, the 13th order and the 14th order of the austenite B type hybrid are calculated too, and their binding energy of austenite are calculated by substituting the formula of the binding energy of Yu Ruihuang, and the best final error compared with the experimental value is less than 1.30%.

A comparative study of high temperature properties of cobalt-free perovskites

Co-free perovskites with chemical composition Ba0.5Sr0.5Fe0.8M0.2O3-δ (M = Ni, Cu, Zn) were synthesized by the modified Pechini method, and their structure and microstructure were characterized by XRD and SEM. Oxygen content, electrical resistivity and Thermal Expansion Coefficient (TEC) were evaluated in air between room temperature and 900 °C. The high-temperature properties of these perovskites were compared with those of Co containing Ba0.5Sr0.5Fe0.8Co0.2O3-δ perovskite. The highest electrical conductivity was obtained for Ba0.5Sr0.5Fe0.8Cu0.2O3-δ, with values of 47.6 Scm−1 at 544 °C. This same composition also exhibits the highest oxygen vacancies concentration: 3-δ = 2.61 at room temperature. In contrast, the Ba0.5Sr0.5Fe0.8Zn0.2O3-δ, showed lower electrical conductivity suggesting that the Zn+2 ions block electron transport. Co-free perovskites seem to be stable at high temperatures for long term periods. However, these compounds suffered degradation at room temperature in samples stored in air.

Experimental Study of High Temperature Properties and Rheological Behavior of Iranian Rock Asphalt

To evaluate the high temperature properties and rheological behavior of Iranian Rock Asphalt(IRA), convectional test and temperature scanning test over modified asphalt containing A-70 asphalt as base asphalt and IRA as different amount were conducted. The results show 1) an increase in asphalt binder’s capability of deformation resistance under high temperature, decreases both in asphalt binder’s temperature sensitivity and low-temperature performance; 2)an increase in anti-rutting factor, a decrease on loss tangent value, an improvement of dynamic viscosity. Thus the asphalt binder’s high temperature performance is greatly improved and anti-rutting capability strengthened.

Graphitic Nanoparticles

Pure carbon materials, graphite and diamond, possess a wide array of interesting physical properties, and so attract a large spectra of interests and applications. Carbon microparticles (carbon black) and carbon fibers are widely used in practical applications including common materials (paints, inks, polymers, etc.) and high-performance composite materials.Carbon displays a remarkably rich and complex chemical behavior (three different possible hybridizations: sp1, sp2, and sp3). In particular, the covalent carboncarbon bond is one of the strongest in nature, and induces a high melting temperature (> 4000°C). The phase changes associated with unusually high temperatures and pressures as revealed in the carbon phase diagram, and the fact that the solid sublimates at low pressures before melting, lead to many experimental difficulties in the study of high-temperature properties of carbon materials. Experiments must therefore rely on transient melting, for example, laser vaporization or arc-discharge heating. This explains why fullerenes and related graphitic structures have only recently been discovered.From a fundamental point of view, the discovery of fullerenes has introduced new ideas about how carbon atoms bond. The curvature and closure of graphitic surfaces has become a standard concept in carbon chemistry, and recently a wide range of structures formed by curved graphitic networks has been observed. A surprising aspect of fullerene research is that these novel graphitic structures were found in well-known experiments, and that they had been overlooked for so many years.This article will describe recent progress in the generation and physical characterization of graphitic nanoparticles, or multishell fullerenes. The lack of an efficient method for producing, as well as a method for purifying these particles makes it difficult to characterize them and to develop possible applications.

Study of high temperature properties of mechanically alloyed aluminium-titanium alloys: K.S. Lee et al (Han Yang University, Seoul, Korea)

Study of high temperature properties of mechanically alloyed aluminium-titanium alloys: K.S. Lee et al (Han Yang University, Seoul, Korea)

Programmed In Situ Melting, Freezing, and Tensile Testing for Laboratory Study of High Temperature Properties of As-Cast Metals

Abstract A technique has been developed for controlled melting and freesing of a steel specimen in a Duffers Gleeble®, combined with a tensile testing capability, in order to obtain subsequent high temperature mechanical properties.